The present invention relates to an ink-jet printer using hot-melt type ink and capable of heating a recording medium such as a paper and cooling the recording medium after the hot-melt type ink has been printed on the recording medium.
A conventional hot-melt type ink-jet printer includes a recording head mounted on a carriage. The recording head includes a nozzle head having a plurality of nozzles, an ink melting section including a heater, and a hopper for storing solid ink pellets. Further, a platen is provided in confrontation with the nozzle head for supporting the recording medium. The carriage is moved in a main scanning direction orthogonal to a recording medium feeding direction, while hot-melt ink droplets are ejected from the nozzles in the nozzle head to form images such as characters and graphs on the surface of the recording medium. The hot melt ink, once printed on a print medium, is extremely durable and has a weather proof characteristic. Hot-melt ink liquefies when heated and hardens at room temperature. Therefore, to print using hot melt ink, the hot melt ink in the print head is heated and melted before it is ejected from the print head.
If the hot-melt ink is ejected from the nozzle heads onto the surface of the recording medium having a relatively low temperature, the ink droplet is immediately solidified at the surface. Therefore, ink fixing property on the recording medium may be lowered. Thus, the solidified ink may be easily peeled off from the surface of the recording medium to degrade the imaging quality. In this connection, the recording medium must be sufficiently heated prior to the ink ejection. To this effect, conveying speed of the recording medium must be low prior to the printing operation to obtain sufficient heat transmission to the recording medium. As a result, high speed printing cannot be performed.
If the hot-melt ink is ejected onto pre-heated recording medium having a prescribed elevated temperature, the fixing properties of the ink on the recording medium can be improved. However, downstream of the recording head, the recording medium continues to be fed between a discharge roller and a pinch roller. If the hot-melt ink fixed on the recording medium has not solidified completely before passing through these rollers, some of the ink is transferred to the pinch roller and the like, thereby reducing the quality of the printed image.
In order to avoid these problems, in a subsequent conventional printer, a heater is provided at a back side of the platen opposite a side along which the recording medium passes for increasing the temperature of the recording medium. Further, a sheet conveying distance between the platen and a discharge section including the discharge roller and the pinch roller is designed to be longer to allow the recording medium just printed to cool while being conveyed over this longer distance. This allows the hot-melt ink to solidify before reaching the discharge section.
However, in order to lengthen the conveying distance, it is necessary to increase the overall dimensions of the printer. Moreover, if the conveying speed of the recording medium is increased after printing operation, the time required to convey the recording medium from the printing portion to the discharge section is essentially decreased. As a result, it is impossible to achieve the cooling effect when performing high-speed printing on a printer of this construction and, therefore, impossible to achieve an image of desirable quality.
Further, in a conventional hot-melt type ink jet printer, a power board is provided in a main case of the printer. Since a temperature of the power board tends to be elevated, a cooling fan is provided in the main case to cool the power board by blowing air on the same. The cooling fan is disposed in a wall of the main case, from which location external air can be easily taken in or expelled.
U.S. Pat. No. 5,005,025 discloses an ink jet printer having a heater whose upstream part serves as a platen and whose downstream part extending to a discharge roller. Because the heater provides an elongated conveying path, sufficient heat can be transmitted to the recording medium for improving fixation.